EP1233299A1 - Monolithically integrated optical component comprising a modulator and a heterojunction bipolar transistor - Google Patents

Monolithically integrated optical component comprising a modulator and a heterojunction bipolar transistor Download PDF

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Publication number
EP1233299A1
EP1233299A1 EP02290296A EP02290296A EP1233299A1 EP 1233299 A1 EP1233299 A1 EP 1233299A1 EP 02290296 A EP02290296 A EP 02290296A EP 02290296 A EP02290296 A EP 02290296A EP 1233299 A1 EP1233299 A1 EP 1233299A1
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European Patent Office
Prior art keywords
optical component
electro
transistor
waveguide
modulator
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EP02290296A
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German (de)
French (fr)
Inventor
Fabrice Devaux
Sylvian Blayac
Philippe Andre
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Oclaro North America Inc
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Alcatel CIT SA
Alcatel SA
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Publication of EP1233299A1 publication Critical patent/EP1233299A1/en
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/015—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on semiconductor elements with at least one potential jump barrier, e.g. PN, PIN junction
    • G02F1/025—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on semiconductor elements with at least one potential jump barrier, e.g. PN, PIN junction in an optical waveguide structure
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/0121—Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
    • H01S5/0261—Non-optical elements, e.g. laser driver components, heaters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
    • H01S5/06203—Transistor-type lasers

Definitions

  • the invention relates to the field of components electronics and electro-optics made on materials with a crystalline structure (III-V materials by example) and intended for use as part of high speed data transmission applications on optical fibers.
  • the invention relates more specifically to a integrated monolithic optical component comprising a electronic element and an electro-optical element, such that a transistor connected to a modulator for a voltage control of the latter.
  • the present invention seeks to improve the performance of the assembly formed by these two electronic and electro-optical elements.
  • a conventional electro-optical modulator includes a stacking of epitaxial layers on a substrate in III-V semiconductor material, usually from InP.
  • the successive layers consist of a layer lower containment, an active layer, and of an upper containment layer, these three layers forming the active waveguide of the component.
  • the active layer is made of a material single undoped quaternary, for example InGaAsP.
  • Containment layers are made of a material III-V, from InP for example, each doped with one type of different carriers, one forming the anode and the other the cathode.
  • the modulator is generally controlled by a voltage source, a transistor for example, whose impedance can reach 50 Ohms.
  • the modulator is not used to the best of its performance and that the width of the operating frequency band of a modulator electro-optics on InP is 5 to 10 times less than that imposed by the intrinsic limits to the material. This is particularly harmful in the context broadband applications with modulators operating between 40 and 160 Gb / s.
  • Another solution proposed in the prior art, consists in achieving a monolithic integration of modulator with the control transistor by integrating the active modulator layer in the structure of the transistor (in the collector layer).
  • the active layer of the modulator is located in the collector depletion area, which, in equivalent diagram, consists in placing the modulator in series of the collector. As there is no longer access at one of the modulator layers, the command is realized in current and no longer in voltage. Such a current control implies a strong resistance of load, which can even be greater than 50 ⁇ . The width modulator bandwidth is therefore not improved.
  • the purpose of the present invention is to provide a integration of the electro-optical component with the element electrical control so as to minimize parasitic resistances and allow operation optimal of said electro-optical component.
  • the invention proposes to use a heterojunction bipolar transistor (HBT) like voltage control source and realize a monolithic integration of the electro-optical component said HBT transistor.
  • HBT heterojunction bipolar transistor
  • the integration of the electro-optical component is located in the layer of sub-collector of the HBT transistor which constitutes advantageously one of the confinement layer of said component.
  • the active structure of the component electro-optics must be widened so that the layer of sub-collector directly constitutes the layer upper confinement of said component.
  • the size of the transistor cannot be reduced below one limit value imposed by the constraints of manufacturing and design is the width of the electro-optical component which must be increased.
  • the invention therefore proposes to extend the area enlarged component active waveguide, area under the HBT transistor, in order to transform this area expanded to a multimode interference coupler having an input waveguide and a waveguide single-mode output.
  • the subject of the invention is more particularly a monolithic integrated optical component comprising a control transistor connected to an electro-optical component having an active waveguide and at least one input waveguide and an output waveguide, characterized in that said transistor is a heterojunction bipolar transistor (HBT) comprising at least one sub-collector layer which is common a confinement layer of the electro-optical component, and in that the active waveguide of said electro-optical component has a structure enlarged located under a contact area of the transistor (HBT) and having substantially the same surface as said transistor.
  • HBT heterojunction bipolar transistor
  • the enlarged structure of the active waveguide is elongated so as to constitute a multimode interference coupler (MMIC).
  • MMIC multimode interference coupler
  • the present invention seeks to reduce the impedance of the control source of an electro-optical component.
  • the invention proposes to integrate said electro-optical component to said source of control constituted by a bipolar transistor with heterojunction (HBT). This integration is good illustrated in the diagram in Figure 1.
  • Bipolar heterojunction transistors 10 are perfectly well controlled in the state of technical. They usually consist of several epitaxial layers on a substrate 100 in III-V semiconductor material, conventionally from InP. The different epitaxial layers are engraved to constitute mesas which define the collector C, base B and emitter E of transistor 10. Des electrical contacts 11,12,13 must be taken from each of the mesas by a deposit of metallic zones (also called contact areas).
  • the heterojunction is between the base B and emitter E, the corresponding layers being made of semiconductor materials different.
  • a base layer B in InGaAs and an InP emitter E layer each doped with different type.
  • Heterojunction authorizes doping very high base and allows the realization of a very fine base. We thus obtain frequencies of very high operation.
  • a bipolar transistor can be single or double heterojunction, the second heterojunction located between the base and the collector according to the same principle of arrangement of epitaxial layer.
  • the collector layer C can be deposited on an intermediate layer of sub-collector SC and not directly on the substrate 100.
  • the sub-collector SC consists of semiconductor material different from that of the collector but doped of the same type.
  • the metal contact 13 of the collector C is then taken on the sub-collector layer SC.
  • the electro-optical component 20 is placed below the control transistor 10, the layer of sub-collector SC of said transistor 10 being used to constitute the upper confinement layer 21 of said component 20.
  • the component electro-optics 20 is a modulator whose guide active wave 25 consists of a layer of upper confinement 21, of an active layer 22 and a lower confinement layer 23 deposited on the substrate 100.
  • the electro-optical component can be, for example, a laser source, photodiode, optical amplifier in semiconductor or other.
  • the active waveguide 25 of the electro-optical component 20 must be widened so that the sub-collector layer SC of transistor HBT 10 constitutes directly the upper confinement layer 21 of said component 20.
  • the width of a guide active wave is much smaller than that of a transistor (about ten times smaller).
  • the size of the HBT transistor 10 cannot be reduced by below a limit value. So this is the width of the electro-optical component 20 which must be increased.
  • the active waveguide 25 of the component electro-optics 20 has an enlarged structure 30 located under the contact area 13 of the HBT transistor 10 and having substantially the same surface as the SC collector layer of said transistor 10.
  • the invention therefore proposes to extend the structure enlarged 30 of the electro-optical component 20 in order to transform into a multimode interference coupler (MMIC) comprising at least one input waveguide 26 and a 27 single-mode output waveguide (MMIC 1x1).
  • MMIC multimode interference coupler
  • Such an extension of the enlarged structure 30 of the electro-optical component 20 necessarily involves a elongation of the sub-collector layer SC of the transistor 10, but it does not affect the good operation of said HBT transistor.
  • the length L MMI of the enlarged structure 30 of the electro-optical component 20 is directly connected to its width W MMI according to the following relationship:
  • the MMI n W MMI 2 / ⁇
  • n the effective index of the waveguide 25, and ⁇ the wavelength of the optical signal propagating in the electro-optical component 20.
  • the electro-optical component 20 and the transistor heterojunction bipolar 10 are integrated on a substrate 100, in semi-insulating InP for example. Integration is achieved by stacking layers successive deposits by epitaxy according to processes well known allowing good thickness control and compositions of each epitaxial layer. This stacking of successive layers is well explained by figure 1.
  • the invention advantageously makes it possible to reduce the series resistance between the electro-optical component 20 and the control transistor 10 by eliminating the parasitic resistances linked to metallic contacts between the two elements.
  • resistance 3 ⁇ series could be obtained.
  • modulator 20 can be ordered by a source of impedance of 10 ⁇ .
  • the width of the bandwidth can be increased by a factor of 2 to 3 compared to the current width, all the others parameters being kept identical. Limits component intrinsics can therefore be approached more.

Abstract

L'invention concerne un composant optique intégré monolithique comprenant un transistor de commande (10) connecté à un composant électro-optique (20) comportant un guide d'onde actif (25) et au moins un guide d'onde d'entrée et un guide d'onde de sortie, caractérisé en ce que ledit transistor (10) est un transistor bipolaire à hétérojonction (HBT) comportant au moins une couche de sous-collecteur (SC) qui est commune à une couche de confinement (21) du composant électro-optique (20), et en ce que le guide d'onde actif (25) dudit composant électro-optique (20) comporte une structure élargie (30) située sous une zone de contact du transistor bipolaire à hétérojonction (10) et présentant sensiblement la même surface que ledit transistor (10). <IMAGE>The invention relates to a monolithic integrated optical component comprising a control transistor (10) connected to an electro-optical component (20) comprising an active waveguide (25) and at least one input waveguide and a output waveguide, characterized in that said transistor (10) is a bipolar heterojunction transistor (HBT) comprising at least one sub-collector layer (SC) which is common to a confinement layer (21) of the component electro-optic (20), and in that the active waveguide (25) of said electro-optical component (20) has an enlarged structure (30) located under a contact area of the bipolar heterojunction transistor (10) and having substantially the same surface as said transistor (10). <IMAGE>

Description

L'invention concerne le domaine des composants électroniques et électro-optiques réalisés sur des matériaux à structure cristalline (matériaux III-V par exemple) et destinés à être utilisés dans le cadre d'applications de transmission de données à haut débit sur fibres optiques.The invention relates to the field of components electronics and electro-optics made on materials with a crystalline structure (III-V materials by example) and intended for use as part of high speed data transmission applications on optical fibers.

L'invention concerne plus spécifiquement un composant optique monolithique intégré comportant un élément électronique et un élément électro-optique, tel qu'un transistor connecté à un modulateur pour une commande en tension de ce dernier.The invention relates more specifically to a integrated monolithic optical component comprising a electronic element and an electro-optical element, such that a transistor connected to a modulator for a voltage control of the latter.

La présente invention cherche à améliorer les performances de l'ensemble constitué par ces deux éléments électronique et électro-optique.The present invention seeks to improve the performance of the assembly formed by these two electronic and electro-optical elements.

Un modulateur électro-optique classique comporte un empilement de couches épitaxiées sur un substrat en matériau semi-conducteur III-V, généralement de l'InP. Les couches successives sont constituées d'une couche de confinement inférieure, d'une couche active, et d'une couche de confinement supérieure, ces trois couches formant le guide d'onde actif du composant. En général, la couche active est composée d'un matériau quaternaire unique non dopé, par exemple du InGaAsP. Les couches de confinement sont composées d'un matériau III-V, de l'InP par exemple, dopée chacune d'un type de porteurs différents et formant l'une l'anode et l'autre la cathode. A conventional electro-optical modulator includes a stacking of epitaxial layers on a substrate in III-V semiconductor material, usually from InP. The successive layers consist of a layer lower containment, an active layer, and of an upper containment layer, these three layers forming the active waveguide of the component. In general, the active layer is made of a material single undoped quaternary, for example InGaAsP. Containment layers are made of a material III-V, from InP for example, each doped with one type of different carriers, one forming the anode and the other the cathode.

Le modulateur est généralement commandé par une source en tension, un transistor par exemple, dont l'impédance peut atteindre 50 Ohms. La fréquence de coupure résultante est alors donnée par la relation : fc = 1 / (2π(RS+RL)Cm). The modulator is generally controlled by a voltage source, a transistor for example, whose impedance can reach 50 Ohms. The resulting cutoff frequency is then given by the relation: f vs = 1 / (2π (R S + R The )VS m ).

Avec RS ≈ 5Ω, la résistance de série du modulateur
   RL, l'impédance de la source de commande
   Cm, la capacité du modulateur.With R S ≈ 5Ω, the series resistance of the modulator
R L , the impedance of the control source
C m , the capacity of the modulator.

Il en résulte que le modulateur n'est pas utilisé au meilleur de ses performances et que la largeur de la bande de fréquence de fonctionnement d'un modulateur électro-optique sur InP est 5 à 10 fois inférieure à celle imposée par les limites intrinsèques au matériau. Cela est particulièrement nuisible dans le cadre d'applications haut débit avec des modulateurs fonctionnant entre 40 et 160 Gb/s.As a result, the modulator is not used to the best of its performance and that the width of the operating frequency band of a modulator electro-optics on InP is 5 to 10 times less than that imposed by the intrinsic limits to the material. This is particularly harmful in the context broadband applications with modulators operating between 40 and 160 Gb / s.

Afin de réduire l'impédance de la source de commande, il a été envisagé de réduire au maximum, voire de supprimer, les transports de charges électriques entre la source et le modulateur. Cela a été tenté en rapprochant physiquement les deux éléments. Cependant, cette solution ne permet pas d'éviter totalement les parasites entre la source et le modulateur. Or, un Ohm de résistance parasite peut entraíner une réduction de la bande passante en dessous de 40 GHz.In order to reduce the source impedance of order, it was considered to reduce as much as possible, or even to suppress, the transport of loads between the source and the modulator. This has been tempted by physically bringing the two together elements. However, this solution does not allow totally avoid parasites between the source and the modulator. However, an ohm of parasitic resistance can cause a reduction in bandwidth below 40 GHz.

Une autre solution, proposée dans l'art antérieur, consiste à réaliser une intégration monolithique du modulateur avec le transistor de commande en intégrant la couche active du modulateur dans la structure du transistor (dans la couche de collecteur).Another solution, proposed in the prior art, consists in achieving a monolithic integration of modulator with the control transistor by integrating the active modulator layer in the structure of the transistor (in the collector layer).

Une telle solution comporte cependant des inconvénients. La couche active du modulateur est située dans la zone de déplétion du collecteur, ce qui, en schéma équivalent, consiste à placer le modulateur en série du collecteur. Comme il n'y a alors plus accés à une des couches du modulateur, la commande est réalisée en courant et non plus en tension. Une telle commande en courant implique une forte résistance de charge, qui peut même être supérieure à 50Ω. La largeur de la bande passante du modulateur n'est donc pas améliorée.However, such a solution includes disadvantages. The active layer of the modulator is located in the collector depletion area, which, in equivalent diagram, consists in placing the modulator in series of the collector. As there is no longer access at one of the modulator layers, the command is realized in current and no longer in voltage. Such a current control implies a strong resistance of load, which can even be greater than 50Ω. The width modulator bandwidth is therefore not improved.

Le but de la présente invention est de proposer une intégration du composant électro-optique avec l'élément électrique de commande de manière à minimiser les résistances parasites et à permettre le fonctionnement optimal dudit composant électro-optique.The purpose of the present invention is to provide a integration of the electro-optical component with the element electrical control so as to minimize parasitic resistances and allow operation optimal of said electro-optical component.

A cet effet, l'invention propose d'utiliser un transistor bipolaire à hétérojonction (HBT) comme source de commande en tension et de réaliser une intégration monolithique du composant électro-optique audit transistor HBT.To this end, the invention proposes to use a heterojunction bipolar transistor (HBT) like voltage control source and realize a monolithic integration of the electro-optical component said HBT transistor.

Selon la présente invention, l'intégration du composant électro-optique se situe dans la couche de sous-collecteur du transistor HBT qui constitue avantageusement une des couche de confinement dudit composant. According to the present invention, the integration of the electro-optical component is located in the layer of sub-collector of the HBT transistor which constitutes advantageously one of the confinement layer of said component.

A cet effet, la structure active du composant électro-optique doit être élargie pour que la couche de sous-collecteur constitue directement la couche supérieure de confinement dudit composant. La taille du transistor ne pouvant pas être réduite en deçà d'une valeur limite imposée par les contraintes de fabrication et de conception, c'est la largeur du composant électro-optique qui doit être augmentée.To this end, the active structure of the component electro-optics must be widened so that the layer of sub-collector directly constitutes the layer upper confinement of said component. The size of the transistor cannot be reduced below one limit value imposed by the constraints of manufacturing and design is the width of the electro-optical component which must be increased.

Cependant, un élargissement du guide d'onde actif du composant électro-optique entraíne la perte de la propagation monomode du signal dans ledit composant. L'invention propose par conséquent d'allonger la zone élargie du guide d'onde actif du composant, zone située sous le transistor HBT, afin de transformer cette zone élargie en un coupleur à interférence multimode comportant un guide d'onde d'entrée et un guide d'onde de sortie monomodes.However, a widening of the active waveguide of the electro-optical component leads to the loss of single-mode propagation of the signal in said component. The invention therefore proposes to extend the area enlarged component active waveguide, area under the HBT transistor, in order to transform this area expanded to a multimode interference coupler having an input waveguide and a waveguide single-mode output.

L'invention a plus particulièrement pour objet un composant optique intégré monolithique comprenant un transistor de commande connecté à un composant électro-optique comportant un guide d'onde actif et au moins un guide d'onde d'entrée et un guide d'onde de sortie, caractérisé en ce que ledit transistor est un transistor bipolaire à hétérojonction (HBT) comportant au moins une couche de sous-collecteur qui est commune à une couche de confinement du composant électro-optique, et en ce que le guide d'onde actif dudit composant électro-optique comporte une structure élargie située sous une zone de contact du transistor (HBT) et présentant sensiblement la même surface que ledit transistor. The subject of the invention is more particularly a monolithic integrated optical component comprising a control transistor connected to an electro-optical component having an active waveguide and at least one input waveguide and an output waveguide, characterized in that said transistor is a heterojunction bipolar transistor (HBT) comprising at least one sub-collector layer which is common a confinement layer of the electro-optical component, and in that the active waveguide of said electro-optical component has a structure enlarged located under a contact area of the transistor (HBT) and having substantially the same surface as said transistor.

Selon une caractéristique, la structure élargie du guide d'onde actif est allongée de manière à constituer un coupleur à interférence multimode (MMIC).According to one characteristic, the enlarged structure of the active waveguide is elongated so as to constitute a multimode interference coupler (MMIC).

Les particularités et avantages de l'invention apparaítront clairement à la lecture de la description qui suit, faite à titre d'exemple illustratif et non limitatif et en regard aux figures annexées sur lesquels :

  • la figure 1 illustre schématiquement l'empilement de couches épitaxiées du composant optique intégré monolithique selon l'invention.
  • la figure 2 est une vue schématique de dessus du composant selon l'invention.
    • The features and advantages of the invention will appear clearly on reading the description which follows, given by way of illustrative and nonlimiting example and with reference to the appended figures in which:
  • FIG. 1 schematically illustrates the stack of epitaxial layers of the monolithic integrated optical component according to the invention.
  • Figure 2 is a schematic top view of the component according to the invention.

    • La présente invention cherche à réduire l'impédance de la source de commande d'un composant électro-optique. A cet effet, l'invention propose d'intégrer ledit composant électro-optique à ladite source de commande constituée par un transistor bipolaire à hétérojonction (HBT). Cette intégration est bien illustrée sur le schéma de la figure 1.The present invention seeks to reduce the impedance of the control source of an electro-optical component. To this end, the invention proposes to integrate said electro-optical component to said source of control constituted by a bipolar transistor with heterojunction (HBT). This integration is good illustrated in the diagram in Figure 1.

    Les transistors bipolaires à hétérojonction 10 (HBT) sont parfaitement bien maítrisé dans l'état de la technique. Ils sont généralement constitués de plusieurs couches épitaxiées sur un substrat 100 en matériau semi-conducteur III-V, classiquement de l'InP. Les différentes couches épitaxiées sont gravées pour constituer des mesas qui définissent le collecteur C, la base B et l'émetteur E du transistor 10. Des contacts électriques 11,12,13 doivent être pris sur chacun des mesas par un dépôt de zones métallique (appelées également zones de contact).Bipolar heterojunction transistors 10 (HBT) are perfectly well controlled in the state of technical. They usually consist of several epitaxial layers on a substrate 100 in III-V semiconductor material, conventionally from InP. The different epitaxial layers are engraved to constitute mesas which define the collector C, base B and emitter E of transistor 10. Des electrical contacts 11,12,13 must be taken from each of the mesas by a deposit of metallic zones (also called contact areas).

    Généralement l'hétérojonction se situe entre la base B et l'émetteur E, les couches correspondantes étant réalisées dans des matériaux semi-conducteurs différents. Par exemple, une couche de base B en InGaAs et une couche d'émetteur E en InP dopée chacune d'un type différent. L'hétérojonction autorise des dopages de la base très élevés et permet la réalisation d'une base très fine. On obtient ainsi des fréquences de fonctionnement très élevées.Generally the heterojunction is between the base B and emitter E, the corresponding layers being made of semiconductor materials different. For example, a base layer B in InGaAs and an InP emitter E layer each doped with different type. Heterojunction authorizes doping very high base and allows the realization of a very fine base. We thus obtain frequencies of very high operation.

    Selon les applications, un transistor bipolaire peut être à simple ou à double hétérojonction, la seconde hétérojonction se situant entre la base et le collecteur selon le même principe d'agencement de couche épitaxiées.Depending on the applications, a bipolar transistor can be single or double heterojunction, the second heterojunction located between the base and the collector according to the same principle of arrangement of epitaxial layer.

    Eventuellement, la couche de collecteur C peut être déposée sur une couche intermédiaire de sous-collecteur SC et non directement sur le substrat 100. Le sous-collecteur SC est constitué d'un matériau semi-conducteur différent de celui du collecteur mais dopé du même type. Le contact métallique 13 du collecteur C est alors pris sur la couche de sous-collecteur SC.Optionally, the collector layer C can be deposited on an intermediate layer of sub-collector SC and not directly on the substrate 100. The sub-collector SC consists of semiconductor material different from that of the collector but doped of the same type. The metal contact 13 of the collector C is then taken on the sub-collector layer SC.

    Selon une caractéristique essentielle de l'invention, le composant électro-optique 20 est placé en dessous du transistor 10 de commande, la couche de sous-collecteur SC dudit transistor 10 étant utilisée pour constituer la couche supérieure de confinement 21 dudit composant 20.According to an essential characteristic of the invention, the electro-optical component 20 is placed below the control transistor 10, the layer of sub-collector SC of said transistor 10 being used to constitute the upper confinement layer 21 of said component 20.

    Dans l'exemple de la figure 1, le composant électro-optique 20 est un modulateur dont le guide d'onde actif 25 est constitué d'une couche de confinement supérieure 21, d'une couche active 22 et d'une couche de confinement inférieure 23 déposées sur le substrat 100.In the example in Figure 1, the component electro-optics 20 is a modulator whose guide active wave 25 consists of a layer of upper confinement 21, of an active layer 22 and a lower confinement layer 23 deposited on the substrate 100.

    Selon d'autres applications de l'invention, le composant électro-optique peut être, par exemple, une source laser, une photodiode, un amplificateur optique en semi-conducteur ou autre.According to other applications of the invention, the electro-optical component can be, for example, a laser source, photodiode, optical amplifier in semiconductor or other.

    Afin de permettre la mise en oeuvre de l'invention, le guide d'onde actif 25 du composant électro-optique 20 doit être élargi pour que la couche de sous-collecteur SC du transistor HBT 10 constitue directement la couche de confinement supérieure 21 dudit composant 20.In order to allow the implementation of the invention, the active waveguide 25 of the electro-optical component 20 must be widened so that the sub-collector layer SC of transistor HBT 10 constitutes directly the upper confinement layer 21 of said component 20.

    En effet, classiquement, la largeur d'un guide d'onde actif est largement plus petite que celle d'un transistor (environ dix fois plus petite). Or, la taille du transistor HBT 10 ne peut pas être réduite en deçà d'une valeur limite. C'est donc la largeur du composant électro-optique 20 qui doit être augmentée.Indeed, conventionally, the width of a guide active wave is much smaller than that of a transistor (about ten times smaller). Now, the size of the HBT transistor 10 cannot be reduced by below a limit value. So this is the width of the electro-optical component 20 which must be increased.

    Ainsi, le guide d'onde actif 25 du composant électro-optique 20 comporte une structure élargie 30 située sous la zone de contact 13 du transistor HBT 10 et présentant sensiblement la même surface que la couche de sous collecteur SC dudit transistor 10.Thus, the active waveguide 25 of the component electro-optics 20 has an enlarged structure 30 located under the contact area 13 of the HBT transistor 10 and having substantially the same surface as the SC collector layer of said transistor 10.

    Cependant, un élargissement du guide d'onde actif 25 entraíne la perte de la propagation monomode du signal dans le composant électro-optique 20. L'invention propose alors d'allonger la structure élargie 30 du composant électro-optique 20 afin de la transformer en un coupleur à interférence multimode (MMIC) comportant au moins un guide d'onde d'entrée 26 et un guide d'onde de sortie 27 monomodes (MMIC 1x1). Un tel allongement de la structure élargie 30 du composant électro-optique 20 implique nécessairement un allongement de la couche de sous-collecteur SC du transistor 10, mais cela ne nuit aucunement au bon fonctionnement dudit transistor HBT.However, a widening of the active waveguide 25 causes the loss of the single mode propagation of the signal in the electro-optical component 20. The invention therefore proposes to extend the structure enlarged 30 of the electro-optical component 20 in order to transform into a multimode interference coupler (MMIC) comprising at least one input waveguide 26 and a 27 single-mode output waveguide (MMIC 1x1). Such an extension of the enlarged structure 30 of the electro-optical component 20 necessarily involves a elongation of the sub-collector layer SC of the transistor 10, but it does not affect the good operation of said HBT transistor.

    En se référant à la figure 2, la longueur LMMI de la structure élargie 30 du composant électro-optique 20 est reliée directement à sa largeur WMMI selon la relation suivante : LMMI = n WMMI 2 / λ Referring to FIG. 2, the length L MMI of the enlarged structure 30 of the electro-optical component 20 is directly connected to its width W MMI according to the following relationship: The MMI = n W MMI 2 / λ

    Avec n l'indice effectif du guide d'onde 25, et λ la longueur d'onde du signal optique se propageant dans le composant électro-optique 20.With n the effective index of the waveguide 25, and λ the wavelength of the optical signal propagating in the electro-optical component 20.

    Sans sortir du cadre de l'invention, on peut envisager d'appliquer l'intégration du composant électro-optique avec un transistor HBT dans un cas où ledit composant aurait N guides d'onde d'entrée et N guides d'onde de sortie monomodes.Without departing from the scope of the invention, one can consider applying component integration electro-optics with an HBT transistor in a case where said component would have N input waveguides and N single-mode output waveguides.

    La réalisation de l'invention fait appel à des procédés de fabrication connus et bien maítrisés dans l'état de la technique.The realization of the invention calls upon known and well mastered manufacturing processes in the state of the art.

    Le composant électro-optique 20 et le transistor bipolaire à hétérojonction 10 sont intégrés sur un substrat 100, en InP semi-isolant par exemple. L'intégration est réalisée par un empilement de couches successives déposées par épitaxie selon des procédés bien connus permettant un bon contrôle des épaisseurs et des compositions de chaque couche épitaxiée. Cet empilement de couches successives est bien explicité par la figure 1.The electro-optical component 20 and the transistor heterojunction bipolar 10 are integrated on a substrate 100, in semi-insulating InP for example. Integration is achieved by stacking layers successive deposits by epitaxy according to processes well known allowing good thickness control and compositions of each epitaxial layer. This stacking of successive layers is well explained by figure 1.

    L'invention permet avantageusement de réduire la résistance série entre le composant électro-optique 20 et le transistor de commande 10 en éliminant les résistances parasites liées aux contacts métalliques entre les deux éléments. En pratique, une résistance série de 3Ω a pu être obtenue. Avec une résistance série aussi faible, le modulateur 20 peut être commandé par une source d'impédance de 10Ω. La largeur de la bande passante peut ainsi être augmentée d'un facteur 2 à 3 par rapport à la largeur actuelle, tous les autres paramètres étant maintenus identiques. Les limites intrinsèques du composant peuvent donc être approchées davantage.The invention advantageously makes it possible to reduce the series resistance between the electro-optical component 20 and the control transistor 10 by eliminating the parasitic resistances linked to metallic contacts between the two elements. In practice, resistance 3Ω series could be obtained. With resistance such low series, modulator 20 can be ordered by a source of impedance of 10Ω. The width of the bandwidth can be increased by a factor of 2 to 3 compared to the current width, all the others parameters being kept identical. Limits component intrinsics can therefore be approached more.

    L'intégration du composant électro-optique au transistor de commande entraíne une dissipation thermique qui peut nuire aux performances dudit composant. En outre, un coupleur MMI induit environ 1dB de pertes optiques. Ces inconvénients sont cependant négligeables en regard des améliorations apportées par la présente invention.Integration of the electro-optical component into control transistor causes dissipation which may affect the performance of said component. In addition, an MMI coupler induces approximately 1dB optical losses. These drawbacks are however negligible compared to the improvements made by the present invention.

    Claims (8)

    Composant optique intégré monolithique comprenant un transistor de commande (10) connecté à un composant électro-optique (20) comportant un guide d'onde actif (25) et au moins un guide d'onde d'entrée (26) et un guide d'onde de sortie (27), caractérisé en ce que ledit transistor (10) est un transistor bipolaire à hétérojonction (HBT) comportant au moins une couche de sous-collecteur (SC) qui est commune à une couche de confinement (21) du composant électro-optique (20), et en ce que le guide d'onde actif (25) dudit composant électro-optique (20) comporte une structure élargie (30) située sous une zone de contact du transistor bipolaire à hétérojonction (10) et présentant sensiblement la même surface que ledit transistor (10).Monolithic integrated optical component comprising a control transistor (10) connected to an electro-optical component (20) comprising an active waveguide (25) and at least one input waveguide (26) and a guide output wave (27), characterized in that said transistor (10) is a bipolar heterojunction transistor (HBT) comprising at least one sub-collector layer (SC) which is common to a confinement layer (21) of the electro-optical component (20), and in that the active waveguide (25) of said electro-optical component (20) has an enlarged structure (30) located under a contact area of the heterojunction bipolar transistor (10) and having substantially the same surface as said transistor (10). Composant optique selon la revendication 1, caractérisé en ce que la structure élargie (30) du guide d'onde actif (25) est allongée de manière à constituer un coupleur à interférence multimode (MMIC).Optical component according to claim 1, characterized in that the enlarged structure (30) of the active waveguide (25) is elongated so as to constitute a multimode interference coupler (MMIC). Composant optique selon la revendications 2, caractérisé en ce que le coupleur à interférence multimode (MMIC) est un coupleur à un guide d'onde d'entrée et un guide d'onde de sortie (MMIC 1x1). Optical component according to claim 2, characterized in that the multimode interference coupler (MMIC) is a coupler with an input waveguide and an output waveguide (MMIC 1x1). Composant optique selon la revendications 2, caractérisé en ce que le coupleur à interférence multimode (MMIC) est un coupleur à N guides d'onde d'entrée et N guides d'onde de sortie (MMIC NxN).Optical component according to claim 2, characterized in that the multimode interference coupler (MMIC) is a coupler with N input waveguides and N output waveguides (MMIC NxN). Composant optique selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le composant électro-optique est un modulateur.Optical component according to any one of Claims 1 to 4, characterized in that the electro-optical component is a modulator. Composant optique selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le composant électro-optique est une source laser.Optical component according to any one of Claims 1 to 4, characterized in that the electro-optical component is a laser source. Composant optique selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le composant électro-optique est une photodiode.Optical component according to any one of Claims 1 to 4, characterized in that the electro-optical component is a photodiode. Composant optique selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le composant électro-optique est un amplificateur optique en semi-conducteur.Optical component according to any one of Claims 1 to 4, characterized in that the electro-optical component is an optical semiconductor amplifier.
    EP02290296A 2001-02-15 2002-02-07 Monolithically integrated optical component comprising a modulator and a heterojunction bipolar transistor Withdrawn EP1233299A1 (en)

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    FR0102100 2001-02-15

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